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Fixed Assets, net - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2016
Property, Plant and Equipment [Line Items]    
Impairments $ 17,386 $ 1,676
Wisdom Tree Japan [Member]    
Property, Plant and Equipment [Line Items]    
Impairments $ 326